This invention relates to adhesive compositions and, in general, curing compositions of the type wherein cure is initiated by means of peroxy compounds such as peroxides or hydroperoxides or by means of ultraviolet irradiation, and takes place by virtue of free radical polymerization. Such compounds typically contain vinyl unsaturation.
It is desirable that compositions of the kind indicated shall be stable in storage for extended periods. Many of these compositions are anaerobic, i.e., undergo cure when deprived of access to oxygen, but can be caused to cure by other means. It is desirable that such anaerobic compositions be preserved from curing when stored in an oxygen-poor environment, in order to undergo cure later, when required, by the use of said other means.
Certain types of compounds are well known as inhibitors of premature polymerization for such compounds. Typically, these inhibitors are quinone- or hydroquinone-type compounds and their derivatives. Free radical scavengers of various types have also been used with some success.
None of these known inhibitors has proven fully satisfactory for all uses, however, especially in connection with acrylate and urethane-acrylate monomers such as those specifically described herein. Inhibitor systems capable of imparting significantly improved stability to free radical curing compositions would thus have great utility.